1. Field of the Invention
This invention relates to a steel column base plate member for connecting a hollow or box-shaped steel column member having square, rectangular or annular section of a steel structure to concrete foundation therefor.
2. Description of the Prior Art
Steel column members of architectural buildings or construction structures are connected to concrete foundations, by means of base plates. It is well known that the steel column is stronger than the concrete of the foundation by a factor of not smaller than 10. To compensate for such difference of the strength between the concrete of the foundation and the steel column, the lower end of the column is joined to a steel plate, and the base plate is secured to the concrete foundation by means of anchor bolts embedded in the concrete foundation.
It has been suggested to provide a base for a column having a recess adapted to accommodate the lower end of the column as shown in U.S. Pat. No. 134,269 issued to J. Gray on Dec. 24, 1872. This base is formed at its center with the recess to reduce its thickness at the center so that the strength against a vertical force may become insufficient to support a load.
It has also been suggested to fit a foot within a lower end of a column which is then inserted into a bed-plate with a sleeve or socket to bring the foot into contact with the bed-plate, disclosed for example as in U.S. Pat. No. 198,072 issued to A. Bonzano on Dec. 11, 1877. This bed-plate will support a vertical force but insufficient to support a bending moment transmitted from the column which will probably been supported by the sleeve.
It has also been suggested to provide a base-socket having a supporting base member and an upwardly projecting portion containing a recess to receive the lower end of a column which is secured within the socket by riveting or the like. Such a socket has been disclosed in the U.S. Pat. No. 1,258,409 issued to T. Hill on Mar. 5, 1918. However, the socket has a configuration prone to give rise to a stress concentration and fails in smooth stress transmission through the socket from the column to a concrete foundation.
It has been proposed to join a tubular member to metal parts wherein the tubular member is fitted within a metal part and a plug or wedge is press fitted in the tubular member. Such a connection has been disclosed in the U.S. Pat. No. 1,488,128 issued to H. P. Macdonald on Mar. 25, 1924. However, this arrangement is not suitable for use in a construction to be subjected to great forces and bending moments.
It has also been proposed to join a tube to a metal part by the use of welding with the aid of beveling portions of the tube. Such a connection of tubing has been disclosed in the U.S. Pat. No. 2,867,036 issued to H. Hovelmann on June 6, 1959. In the method, however, it is required complicated machining for providing the beveling for welding which will increase cost of the connection.
Generally speaking, the base plate member is required to fulfill the following conditions.
1. Since the base plate will be subjected to various severe forces resulting from axial force, shearing force and bending moment acting upon the column member, the base plate must be in configuration to avoid any stress concentration and perform a smooth stress transmission from the column member to the foundation.
2. In order to decrease the cost of a construction as a whole, the working of column member should be minimized only to cutting of both ends thereof. If any grooves for welding are required, the base plate member should be formed with such grooves by the use of means of minimum possible cost.
3. If utilizing any welding method for connecting the base plate member to a column member, the base plate member should be of a configuration capable of applying the most effective welding method which is higher in reliability, minimum of consumed welding rods and carried out with ease. The configuration is also applicable of a best welding method of which characteristic meets stresses derived from forces and bending moments to which the column member is subjected.
4. The base plate member should be a configuration in agreement with a stress distribution acting thereupon resulting from axial and shearing forces and bending moment to which the column member is subjected.
5. The base plate member should be such a configuration that a base portion of the base plate member in contact with a concrete foundation will not be affected by heating derived from welding of the plate member with the column member.
6. The base plate member should be economical of manufacture and serve to decrease the cost of a construction as a whole.